Portion of a chair



FIG. 1 is a perspective view of a first embodiment of a portion of a chair showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a perspective view of a second embodiment of my design.

The broken lines in the drawings form no part of the claimed design. 

The ornamental design for a portion of a chair, as shown and described. 